Chronic Lymphocytic Leukemia (CLL) is a B-cell lymphoproliferative disorder primarily involving the bone marrow, blood and lymph nodes. CLL is the most common type of leukemia in adults and although median survival can be quite long, between 8-12 years, most eventually succumb to their disease. The evidence for a genetic component to CLL is compelling but remains unknown, and is likely complex. However, opportunities to identify underlying variants are apparent -both by varied and unique study and analysis designs and via collaborative efforts. The research plan we propose is multifaceted, highly collaborative and includes several innovative techniques. We will pursue two study designs, each powerful to identify susceptibility genes with different underlying genetic models: high-risk pedigree-based shared genomic segment analysis and case- control association analyses. Genome-wide shared genomic segment analysis is a new method that requires extremely extended, high-risk pedigrees which are available only to researchers with genealogic resources, such as Utah. Our strategy for association will be both genome wide and candidate region. Ascertainment will involve two sites (Utah and Sheffield, UK) and will include both a discordant family-based element (Utah) and a population-based sample (UK). This approach exploits both the increased power of familial cases with the perspective of population-based samples. We are able to pursue these together due to software that we have developed. In addition to conventional analyses, we will develop new methods for the high-risk pedigree and case-control settings: homozygosity mapping in the high-risk pedigrees and case-control SGS and homozygosity mapping. Both conventional and novel methods will be performed as part of broader collaborative efforts. The resource that we will build is timely. CLL genetic research is still in its infancy. The concurrent development of these designs defines an extensive strategy for identifying regions of the genome harboring CLL susceptibility genes and will afford us the opportunity to play a significant role in shaping the direction of CLL genetic research. Particularly, Utah pedigrees, through their structure and high-risk nature, add a previously unrealized aspect to the global picture. If one design or collaborative effort can identify even a single susceptibility gene for CLL, we will have made an important and critical discovery in the etiology of CLL. Such a discovery would not only help our understanding of the etiology of CLL, but also may provide information about other lymphoproliferative disorders and may translate to other cancers. PUBLIC HEALTH RELEVANCE: This project is likely to lead to the identification of one or more genes predisposing to chronic lymphocytic leukemia (CLL). The individual public health implications are: the significantly increased accuracy that could be accomplished in risk estimation for CLL post-gene-identification and, in particular, identification of CLL precursors, insight into the overlapping genetic etiologies of CLL and other lymphoid neoplasms, and the potential improved ability for clinical decision making (for cases and gene carriers) based on genotype. The wider public health implications include the increased understanding that knowledge of any CLL predisposition gene will provide towards underlying the disease mechanism and direction towards the identification of additional predisposition genes.